1. Field of the Invention
The present invention generally relates to alarm control systems for engines. More specifically, the present invention relates to alarm control systems for lubrication systems of engines of outboard motors.
2. Description of Related Art
Outboard motors pose unique challenges to engine designers due to their orientation and the rotation of the engines about a tilting and trimming axis during operation. One such challenge involves supplying lubricant to the moving components of the engine during a variety of operating conditions. Because the orientation of the engine changes during use, accurately sensing a level of lubricant remaining in an lubricant pan becomes difficult, if not impossible. Accurate monitoring of the lubricant is desirable to ensure that the engine is not run dry of lubricant because of a leak or a clogged passage.
In some outboard motors, the engine has a pressure sensor that detects a decrease in lubricant by evaluating the operating pressure within the lubrication system. If the pressure falls to a level indicative of a malfunction, then a buzzer or other alarm immediately sounds. One difficulty in such sensors is determining whether the low pressure is indicative of an actual problem or, rather, is indicative of a sudden change in operating conditions. For instance, due to the viscous nature of oil as a lubricant, the pressure of the lubricant does not vary as rapidly as engine speed. Accordingly, upon rapid acceleration, the lubricant pressure may incorrectly indicate a low pressure and a nonexistent malfunction.
Some engine designers have remedied these false alarm problems by setting the sensor to indicate a problem only when the pressure falls below a minimum pressure that corresponds to an adequate supply of lubricant during idle speed operation.